It is frequently desirable in the well logging art to provide means for combining logging data from two separate and distinct data base sources, which may correspond to digital logging tapes from separate logging operations, into one convenient composite form for purposes of display, further analysis, data processing, and the like.
For example, during one pass through the borehole, one logging tool of a multiple-tool string may fail or yield erroneous data either throughout the entire logging operation or in part over a particular increment of borehole resulting in loss of data. It may be desirable to replace this lost data with data from another logging run and tape. Thus, the valid data residing in the first logging tape and the replacement data on the other logging tape (derived during a different pass through a borehole and corresponding to the same logging parameter data over the borehole increment in which data from the first tape was determined to be erroneous or non-existent) will be retrieved and stored as a composite in a third tape.
As yet another example, logging data is at times derived during separate logging operations over respectively different increments of borehole and stored in separate logging tapes corresponding to the respective logging operations. It may thus be desirable to electronically and functionally splice the data together into a single output file or tape, thereby providing a composite of logging data over the combined borehole increments of the two logging operations.
As yet a third example, in some cases logging parameters are derived during one pass through the borehole which differ from those derived during a different pass and it is desirable for purposes of analysis and the like to merge the data from the two logging operations together into the aforementioned single composite output tape whereby, for example, at a given borehole elevation all of the parameters derived by both logging operations are available. Such derivation of differing parameters during separate logging operations may be due to a number of reasons such as size constraints on the logging string preventing tools for measuring all desired parameters being interconnected for one pass through the borehole, similar constraints regarding tool combination compatibilities, and the like.
Techniques have been available for performing the aforementioned functions of replacing, splicing, or merging digitized logging data from two logging tapes into a single convenient output tape, however these techniques have suffered from serious problems, particularly with respect to field applications wherein wellsite production of composite tapes is particularly desirable.
One of the drawbacks with the prior techniques was that typically separate and distinct programs were provided for performing each of the aforementioned functions of merging, splicing, or replacing of logging data at a computing center remote from the wellsite to which digitized well logging tapes were routed for such processing from the field after the logging operation. Accordingly, no provision was made for a generalized and automated program and method, simplified for difficult field environments, for combining these separate data sets or logging tapes into a composite form on one output tape or file at the wellsite, wherein one of a plurality of such composites such as merging, splicing, or replacing, could be elected on-site and immediately produced from the general program without the need for locating, loading, and the like of separate and distinct programs for performing the particular compositing function elected.
Yet another problem with providing a generalized system for performing one of a variety of compositing functions such as the aforementioned merging, splicing, or replacing, is that differing constraints arise with respect to compatibility of parameters and borehole increments selected from each of the two data bases for compositing, dependent upon the particular option elected.
For example, in the case of replacing data of one data set with data from the remaining data set, it is obviously required that the replacement data and data to be replaced be derived over identical borehole elevations and that the data from the two data sets correspond to identical logging parameters. On the other hand, with respect to the functional splicing of one data set to that of another data set, as also previously described, while it is readily apparent that it is desirable for the logging parameters to be identical for which data is to be spliced, it is further generally desirable that the logging parameter data from the two data sets to be spliced not overlap with respect to the increments of borehole over which they were derived. This is due to the fact that the splice option involves appending one set of logging data derived over one borehole increment in tandem fashion with that of another data set derived over a different borehole increment.
Finally, due to the aforementioned function of the merging operation in which it is desired to develop a composite logging tape comprised of logging parameters derived over a given borehole increment residing in one tape with different parameters derived over the same borehole increment residing in another tape, while an overlapping of such borehole increments is desirable, it is not desirable to permit identical parameters to be selected for merging from each of the data sets in that two measurements of the same logging parameter would thus appear in the output tape at the same borehole elevation.
It can thus be appreciated that it was highly desirable to provide a generalized system for providing composites of logging data from two logging data sets wherein the particular composite was selectively variable from a plurality thereof including merge, replace, and splice options. Yet, it can further be appreciated from the foregoing, that, due to the variety of differing constraints as to compatibility of parameters and borehole increments of the two data sets, which vary as a function of the particular option selected, there was a further need for such a system which could automatically adapt to the type of composite desired, to insure compatibility checks were selected as a function of the particular composite option selected.
The disadvantages of the prior art including those hereinabove recited are overcome by the method for generating variable well logging data composites of the present invention.